Difficulties / tricks in soldering connectors on LiPo
I was greedy and bought old LiPos a year ago in the “PILOTAZH” that sells them, moreover, they had already run out of running connectors, they were left with small cylindrical ones. Well, okay, I thought, I'm soldering.
A surprise for me was the material of the wires, the feeling that they are iron with fiber. color dark grey. They had to be bitten off from the connectors, because they were crimped, the diameter is healthy, and they are soldered only with acid, and even then not very willingly.
Is it like that for everyone? Or just old ones. big on 4s 5000mah I resoldered leaving 1/2 of the wire on the XT60 connector. 1800 are still untouched.
Question: what kind of material is it, with what it needs to be soldered, or are there special connectors for crimping?